The determination of the intestinal lactose activity is of importance in paedriatrics and gastroenterology and may be directly carried out, parting from a mucous sample, or indirectly, parting from the level of glucose in the blood or from the expired hydrogen, after the administration of a dose to the individual.
The direct determination has the disadvantage of constituting a complex and expensive method since it requires specific instruments and very specialized personal for the technique of extraction of the sample which must be submitted to subsequent analysis, apart from its being disagreeable nad not lacking in danger to the individual.
The indirect determination has the advantage of being a technique involving blood, which requires the extraction of blood by a specialied person before the sample may be analyzed, apart from being complex and susceptible to errors, due to the existance of glucose originating from the digestion of other food taken by the individual, and of endogenous glucose which might have been mobilized.
Other methods of determination of the intestinal lactase are based on the fact that specific disaccharides are, based on their affinity to the lactase, subsceptible of acting as substrate of the lactase and transform, by the action of the enzyme, into specific monosaccharides which are absorbed easily by the intestine and eliminated through urine.
Thus, the methods disclosed in Spanish Patentes ES-P-478590 and ES-P-482073, are based on the evaluation "in vivo" by means of the oral administration of 3-O methyl lactase and the analysis of the 3-O-methyl-D-glucose in urine. However, said methods present the disadvantage that they require the employment of a chromatographic procedure for the detection of 3-O-methyl-D-glucose in urine, which implies complex and expensive facilites and analysis equipments.
On the other hand, in Spanish Patent ES-P-9001680 discloses the preparation of disaccharide 4-O-.beta.-galactopyranosyl-D-xylose of formula (I) ##STR1## for the evaluation of the intestinal lactase activity. Said disaccharide is administrated orally, it acts as substrate of the intestinal lactase and decomposes, in the intestinal tract, in xylose and galactose, absorbing the xylose and eliminating through urine where it may be directly evaluated by means of a simple colorimetric method. The disaccharide of Spanish Patent ES-P-9001680, presents the disadvantage that it presents, in spite of having a quite similar structure to that of the lactase, an enhanced affinity to the lactose. This implies that only a part of the digested 4-O-.beta.-galactopyranosyl-D-xylose, is hydrolized based on the enzymatic activity of the lactase and, therefore, the non decomposed part in xylose and galacatose is eliminated with the feces. This implies a relatively substantial margin of error in view that the low or even non existant values of the xylose in the analyzed urine, may originate both from the deficient or zero intestinal lactase activity and from a deficient hydrolization of the disaccharide due to its lack of affinity to the lactase. In order to relieve said margin of errors, it is necessary that the individual digest a substantial quantity of disaccharides, which in turn may lead to intestinal problems such as diarrhea and the corresponding discomforts to the individual.
Spanish Patent ES-P-9001680 also discloses a method of preparation for the 4-O-.beta.-galactopyranosyl-D-xylose, which basically comprises a synthesis parting from benzyl-.beta.-D-xylopyranoside and which follows operational sequences which imply selective protection reactions, glycosylation and desprotection. Both the number of reaction stages, the use of expensive reactive agents such as silver triflate in the glyxosylation reaction, and the employment of chromatographic columns in the purification of intermediates and the final product, produce costs and present difficulties for the performance of said procedure at industrial scale.
On the other hand, Gorin et al. in "The Synthesis of .beta.-Galacto- and .beta.-Gluco-Pyranosyl disaccharides by "Sporobolomyces Singularis", Can. J. Chem. 42(1964) 2307-2319, discloses the synthesis of a plurality of disaccharides, among which are the 2-O-.delta.-D-galactopyranosyl-D-xylose and the 3-O-.delta.-D-galactopyranosyl-D-xylose, by means of a purely experimental procedure. In this publication, the conclusion is reached that the products resulting form the transference of galactosyl, in the use of various acceptors, originate mainly more from the substitution of the secondary hydroxyl groups than from the primary hydroxyl groups, the minimum structural requirement for the reaction with an acceptor seeming to be the hydroxyl adjacent to the substituted hydroxyl group. However, in this publication, no use of the diverse synthetized disaccharides are disclosed.